1. Field of the Invention
The present invention relates to sensor arrays, methods for manufacturing the sensor arrays, and ultrasonic diagnostic apparatuses incorporating the same. More particularly, the invention relates to sensor arrays such as ultrasonic probes used in ultrasonic diagnostic apparatuses, ultrasonic microscopes, metal flaw detecting apparatuses, and the like.
2. Description of the Related Art
Concerning the background of the present invention, an ultrasonic probe used in a conventional ultrasonic diagnostic apparatus will be described. For example, there is an ultrasonic probe disclosed in IEEE Transactions on Utltrasonics, Ferroelectrics, and Frequency Control, Vol. 44, No. 2, March 1997 Hybrid Multi/Single Layer Array Transducers for Increased Signal-to-Noise Ratio.
FIG. 7 is a perspective view showing the main part of an ultrasonic probe used in the conventional ultrasonic diagnostic apparatus. FIG. 8 is a perspective view showing a piezoelectric oscillator used in the ultrasonic probe. An ultrasonic probe 1 shown in FIG. 7 includes a substrate 2 formed of an acoustic absorber regarded as a backing member. A plurality of piezoelectric oscillators 3 is fixed on one main surface of the substrate 2 in a matrix form.
As shown in FIG. 8, the piezoelectric oscillators 3 include a plurality of laminated piezoelectric layers 4. Inner electrodes 5 are formed between the piezoelectric layers 4. An outer electrode 6 is formed on each of the top and bottom surfaces of the laminated piezoelectric layers 4. In addition, on both ends of the laminated piezoelectric layers 4, via-holes 7 are formed. Connecting electrodes 8 are formed inside the via-holes 7. Every other layer of the laminated piezoelectric layers 4 is polarized in a reverse thickness direction. The piezoelectric oscillators 3 are bonded onto one main surface of the substrate 2 by adhesive in such a manner that the main surfaces of the piezoelectric layers 4 are parallel to the main surface of the substrate 2.
Furthermore, on the plurality of piezoelectric oscillators 3, an acoustic matching layer 9 is formed to obtain acoustic matching with a human body. On the acoustic matching layer 9, an acoustic lens 10 is formed to converge ultrasonic beams.
In the piezoelectric oscillators 3 used in the above ultrasonic probe 1, the inner electrodes 5 are extracted by the via-holes 7 and the like. However, alternatively, as the structure and method for extracting the inner electrodes, there is a structure and method for extracting the inner electrodes from side surfaces of the piezoelectric oscillators 3, as usually seen in multi-layer capacitors and the like.
Since each of the piezoelectric oscillators 3 used in the above ultrasonic probe 1 shown in FIG. 7 has a multi-layer structure, good functionality and high-resolution capability can be achieved, so that high sensitivity can be obtained. When the piezoelectric oscillators 3 are manufactured, via-holes need to be formed with high processing precision and electrodes need to be formed with high printing precision. As a result, due to shrinkage occurring when a member is burned, it is difficult to obtain linearity between the via-holes, and it is also difficult to cut the burned member in a matrix form. In addition, after cutting, outer electrodes easily fall off. Therefore, in order to manufacture the piezoelectric oscillators 3, extremely high manufacturing precision is necessary. Since there are many problems in terms of manufacturing, variations in characteristics easily occur.
Similarly, when the inner electrodes 5 of the piezoelectric oscillators 3 are extracted from the side surfaces in the ultrasonic probe 1, a high processing precision is required in manufacturing.
Accordingly, it is an object of the present invention to provide a sensor array that is highly sensitive and capable of being easily manufactured.
It is another object of the present invention to provide a method for manufacturing the above sensor array.
In addition, it is another object of the present invention to provide an ultrasonic diagnostic apparatus using the above sensor array.
The present invention provides a sensor array including a substrate and a plurality of piezoelectric oscillators fixed on a main surface of the substrate in a matrix form. Each of the plurality of piezoelectric oscillators includes a plurality of piezoelectric layers laminated in a direction parallel to the main surface of the substrate, inner electrodes disposed between the plurality of piezoelectric layers, and outer electrodes formed on end faces of the plurality of piezoelectric layers.
The present invention provides a method for manufacturing the above sensor array. The method includes the step of forming a multi-layer structure in which a plurality of piezoelectric layers and a plurality of inner electrodes are laminated, the step of forming a motherboard by cutting the multi-layer structure in the laminated direction, the step of forming outer electrodes on both main surfaces of the motherboard, the step of fixing the motherboard on one main surface of a substrate, and the step of cutting the motherboard to yield the plurality of piezoelectric oscillators.
The present invention provides an ultrasonic diagnostic apparatus including an ultrasonic probe, wherein the ultrasonic probe includes the above sensor array.
In the sensor array according to the present invention, since the piezoelectric oscillators having the multi-layer structure are used, high sensitivity can be obtained.
In addition, as described above, this sensor array can be manufactured by forming the multi-layer structure in which the plurality of piezoelectric layers and the plurality of inner electrodes are laminated, forming the motherboard by cutting the multi-layer structure in the laminated direction, forming the outer electrodes on the main surfaces of the motherboard, fixing the motherboard on one of the main surfaces of the substrate, and cutting the motherboard into the plurality of piezoelectric oscillators. As a result, when the motherboard is fixed on the substrate, since the outer electrodes are formed on the entire main surfaces of the motherboard, no high precision for determining positions is necessary. Thus, this method permits manufacturing of the sensor array to be facilitated.